Mineral oil burner



Dec. 23, 1969 a. SBORLINO 3,485,452

MINERAL OIL BURNER Filed Sept. 19, 1967 INVENTOR. 6W0 SBQKLINQ BY Made M1 United States Patent MINERAL OIL BURNER Gino Sborlino, Milan, Italy,assignor to Ioro & Pansim, Milan, Italy, an Italian company Filed Sept.19, 1967, Ser. No. 668,892 Claims priority, application Italy, Sept. 24,1966, 22,809/ 66, Patent 781,692 Int. Cl. Bb 7/12 U.S. Cl. 239-417 1Claim ABSTRACT OF THE DISCLOSURE A burner for liquid fuel having acentral jet of auxiliary air surrounded by an atomizing air jet issuingfrom a gap between an outer noncylindrical stationary pipe and an innernoncylindrical tubular body, in which gap the fuel is injected, theswitch of said gap being adjustable by moving the said tubular bodyaxially.

This invention relates to a burner for liquid fuels, more particularlymineral oil, of the kind in which the atomization of oil is obtained bya jet of low pressure air.

Burners of the kind referred to above are employed, for example, forheating large rotary-drum dryers within which the inert substancesintended to make up the bitumen mixes for road surfacing are dried. Inthese burners the air blown under a low pressure is generally dividedinto two concentric jets, one of which is intended to atomize the oil assprayed by specially provided nozzles, whereas the other jet suppliesthe secondary air which is necessary to ensure a proper formation of theflame. Ina few burners, the atomization is brought about a central airjet surrounded by a jet of secondary air. Such an arrangement, however,has the defect that the flame shows a tendency towards expansion so asto find in the surrounding annularly shaped jet the air which isnecessary for combustion, it being usually preferred, in the aboverecalled applications, that the flame is mainly developed lengthwise andis so maintained away from the drum walls, to prevent damages thereto.The inventive burner is of the kind in which the atomization of fuel oiltakes place by virtue of a jet having an annular cross-sectional shape,Within which the central jet of secondary air is located. In suchburners, the flame tends to be concentrated about said central jetwithout being radially scattered.

A principal object of the present invention is to provide, in a burnerof the kind last referred to, a satisfactory rate of flow for theatomizing air jet with a rate of flow of fuel oil which can be variedwithin a reasonably wide range, all this without significantly varyingthe rate of flow of secondary air.

This object could be acheived by varying the pressure of the air whichfeeds the atomization jet.

The last mentioned solution, however, would lead to shortcomings of atwofold nature; in the first place, it would require two feed mains withair at different pressures, the constructional intricacy involved beingapparent and, in the second place, a variation of the rate of flow ofthe atomizing air would be thus obtained concurrently with and becauseof a variation in the speed of the atomizing air jet, so that asatisfactory atomization could not be obtained irrespective of the rateof flow.

A particular object of the present invention is to provide a burneroperable at low pressures with a central jet of secondary air surroundedby an atomizing air jet, in which the rate of flow of the atomizing jetcan be varied to suit a variable rate of flow for the fuel oil, stillwithout varying the speed of the atomizing air and without varying therate of flow of the central jet of secondary air.

To achieve this object the inventive burner comprises a pipe whose frontend is open and which is fed from the rear by a source of pressurizedair and containing in its front end a tubular piece leaving a gapbetween itself and the tube, said tubular piece being connected to aduct fed with pressurized oil which opens into said gap through aplurality of openings, and is characterized in that the inner surface ofthe front end of said tube and the outer surface of said tubular piecehave a variable cross-sectional area, means being further provided forvarying the mutual position between the front end of said tube. and saidtubular piece in an axial direction.

This feature, and other additional ones, along with the advantagesafforded thereby, will be more clearly understood from the ensuingdisclosure of an exemplary embodiment as illustrated in the accompanyingdrawing which is a diagrammatical lengthwise section thereof.

The burner shown in the drawing comprises a baseplate 1, internallyhollowed out, which is extended into a tubular portion 2 containing themembers for dividing and delivering the primary :air and for deliveringthe oil.

These members comprise a tubular piece 3 inserted into the end of thepart 2, whose inner surface has a circular cross-section of variablediameter, as shown in the drawing: more detailedly, starting from theinterior of the body 1, said cross-sectional area is graduallydecreased, to be then increased and decreased once again, it beingterminated by a short substantially cylindrical portion which isconfined by a sharp outlet edge.

Within the body 1 is axially and slidably supported a tube 4 by means ofthe bush 5 and a few fins 6 whose projecting portions 7 slide on theinner surface of the portion 2.

One end of the tube 4 is within the tubular piece 3: on said end ismounted also a piece 8, also of tubular shape, connected to the tube 4by spokes 9 in which thin ducts 10 are formed, which communicate withthe end of the tube 4 and open out of the piece 8, where the latter hasits highest diameter, in the gap 11 between the pieces 8 and 3.

The shape of the outer surface of the piece 8 is not cylindrical, but ithas cross-sectional areas whose diameters vary, roughly with the sametrend with which the cross-sectional area of the cavity of the piece 3varies. As a consequence, the thickness of the gap 11 is roughlyconstant when the piece 8 is in the position shown in the drawing,whereas it can be throttled, to a larger or lesser extent, by axiallydisplacing the piece 8.

The other end of the tube 4 which comes out of the body 1 through thebush 5 carries a sleeve 12 which is externally splined and which mesheswith a gear 13: thus the latter, by being rotated, can cause the tube 4to be axially shifted. To this end of the tube 4 is connected a hose 14connected to a source of pressurized oil via a valve 15. This valve isopened more or less by any conventional control, diagrammatically shownat 16 in the drawing. This valve is controlled by a lever 17 connectedthrough a rod 18 to a lever 19 fixed to said gear 13.

The body 1 has a lower aperture which can be totally or partially closedin an adjustable way by a conventional valve which is depicted in thedrawing by two symmetrical vanes 20 pivoted at 21. This opening is fedby air at a comparatively low pressure, that is, in the order of onemeter of column of water, by a blower which has been omitted from thedrawing for the sake of clarity.

The burner as described above operates as follows.

Mineral oil, fed through the valve 15 via the tube 14 to the tube 4,comes out in the form of tiny jets from the ducts 10 into the gap 11.Concurrently, air blown into the body 1, guided by the fins 6, entersthe piece 3 and is divided into two streams: one stream enters the piece8 and passing through the openings or spaces between the spokes 9 comesout in the form of a central jet from the piece 3, whereas the otherstream enters the gap 11 and comes out also from the piece 3 in the formof a tubular jet which wraps the central jet aforesaid. This latterportion of air fulfils the task of atomizing the mineral oil issuingfrom the ducts 10.

When the tube 4, and concurrently therewith the piece 8, are axiallydisplaced, the cross-sectional area of the gap 1} is more or lessthrottled in the vicinity of the outlet of the ducts 10. Inasmuch as thepressure of the air which is fed to the gap 11, assuming that the valve20 is at stand-still, is always virtually constant and equals thepressure fed into the interior of the body 8, the result is that, byshifting the tube 4 axially by rotating the gear 13, the rate of flow ofthe atomizing air, which is just the air flowing through the gap 11, canbe varied without varying the feeding pressure and thus maintain itsoutflow speed, and also its atomizing efliciency, virtually unaltered.

It is also possible to cause said variation of the rate of flow ofatomizing air to be in a preselected relationship with the rate of flowof the fuel oil fed by the valve 15 by properly adjusting the gear ratioobtained with the linkage 17, 18, 19 which bounds the tube 4 axially,and thus the piece 8 relative to the piece 3, to the position of theregulator 16 which controls the valve 15.

It is thus possible to adopt the optimum ratio of oil to atomizing airthrough a wide range of rates of flow of fuel oil. The central jet ofsecondary air which flows in the interior of the piece 8, conversely, iskept at a substantially constant rate of flow and speed, and thus alsoits shape remains virtually the same irrespective of the variations ofthe jet of surrounding air which contains atomized fuel.

The adjustment of the rate of flow of oil and atomizing air can, ifdesired, be servoed to certain factors which are inherent in thecombustion run, for example by a thermometric member such asdiagrammatically shown at 22.

It is understood that the exemplary embodiment shown herein can bevariously modified: for example the position of the tube 4 and of thepiece 8 could be maintained unvaried and the piece 3 could be madeaxially displaceable within the part 2.

I claim:

1. A burner for liquid fuels comprising a tube with an inner surfacehaving a cross-section which is variable along the axis of said tube, atubular piece within said tube and coaxial therewith, with an outersurface having a cross section which is variable along said axis, a gapbetween said tubular piece and said tube, a conduit for the fuel withinsaid tubular piece terminating into a plurality of perforations on theregion of greatest crosssection of the outer surface of said tubularpiece, means for conveying compressed air to one end of said tube,whereby said air passes through said tubular piece and through said gap,and means for displacing said tubular piece axially with respect to saidtube.

References Cited UNITED STATES PATENTS 2,531,538 11/1950 Smith 239-417 X3,091,283 5/1963 Kidwell 239-4l7 X M. HENSON WOOD, JR., Primary ExaminerM. Y. MAR, Assistant Examiner U.S. Cl. X.R. 239-4173F'YiB'ZBARZANO8cZANARDO( G SBORLINO 668, 892 )N5WG2hn7O age T NEEDSTATES PATENT OFFICE CERTEFECATE OF CORRECTEQN Patent No. 3, 5, 452Dated December 23, 1969 Inventor(5) GinO It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

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WILLIAM E- SOHUYLER, JR.

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